Our proposal to elucidate the regulatory factors associated with the biosynthesis, degradation and action of PGs in the skin is yielding interesting findings. For instance (1) we have demonstrated the activity of PGE2-9-ketoreductase in the skin preparations. The activity of this enzyme is increased in proliferating skin tissues such as in psoriatic plaques and in EFA-deficient rats. The significance of this alteration will be investigated further. It is also interesting that the activity of this enzyme is under the regulation of hormonal and non-hormonal agents. (2) The activity of phospholipase A2 has also been demonstrated in skin membrane preparations. The role of this rate limiting enzyme (which catalyzes the releases of precursor arachidonic acid from skin phospholipid) under a variety of conditions is under investigation. It is hoped that results from studies of these two important enzymes will provide us information on the factors regulating the release of precursors for prostaglandin biosynthesis in the skin, their metabolism and perhaps some of the functional roles of prostaglandins in the pathophysiology of the skin.